Lara's brilliance kept the home side on target for a decent score after he plundered 176 out of the West Indies total of 292 for seven at the close.
"The pitch was good for batting but we were pegged back early," Lara told a news conference.
"Fortunately, Shivnarine (Chanderpaul) and I, and then Dwayne (Bravo) and I were able to put partnerships together."
The home side, who won the toss and chose to bat, slumped to 12 for three in the seventh over before Lara and Chanderpaul steadied the innings with a stand of 138 for the fourth wicket.
Bravo then helped Lara add 115, a record West Indies sixth-wicket stand in Tests against South Africa.
In the third over before the close, Lara dragged a delivery from Andre Nel onto his stumps and six balls later, Bravo edged paceman Monde Zondeki to Graeme Smith at first slip to be dismissed for 26.
"I'm disappointed because our plan after tea was not to lose another wicket," Lara said. "We shouldn't be in this position, it's a perfect batting track."
Nel took three wickets for 54 and had praise for the pitch as well as for Lara.
"We were looking forward to bowling here and it worked out well for us at the start," Nel said.
"Brian played unbelievably well, sometimes it's scary bowling to him.
"But he's got two arms and two legs like everybody else and my job is to get him out for my country."
Nel was hoping to see a better batting display from South Africa than the hosts on Friday.
"It was good to pick up a couple of wickets at the end, but it's a great wicket to bat on," Nel said.
"We need to get them out early and try to bat only once."
